class Turtle:
    def __init__(self, x):
        self.num = x


class Fish:
    def __init__(self, y):
        self.num = y


class Pool:

    def __init__(self, x, y):
        self.turtle = Turtle(x)
        self.fish = Fish(y)

    def print_num(self):
        print("水池里有%s只乌龟，%s只鱼。" % (self.turtle.num, self.fish.num))


pool = Pool(4,5)
pool.print_num()
